Seasonal Climate Outlook Message for December 2008 to March 2009

The bottom line

Based on the monthly SOI values recorded for October of plus 14.2 and for November of plus 17.4, the SOI has remained in a Consistently Positive phase.

An analysis of historical rainfall records and a Consistently Positive SOI phase at the end of November, indicate a reasonable 60 to 80% chance of getting above median rainfall during December through to the end of February throughout the eastern third of Queensland (east of a line running from the bottom of the Gulf of Carpentaria through to the central Darling Downs). There is a 40 to 60% chance of getting above median rainfall for December to February throughout the rest of the state .

For example Bundaberg has an 80% chance of getting above its December to February median rainfall of 405mm, Proserpine has a 75% chance of getting above its December to February median rainfall of 855mm, Charters Towers has a 73% chance of getting above its December to February median rainfall of 335mm, Toowoomba has a 68% chance of getting above its December to February median rainfall of 353mm, Yuleba has a 65% chance of getting above its December to February median rainfall of 220mm and Longreach has a 55% chance of getting above its December to February median rainfall of 190mm.

For more information on historical rainfall data for your region try Rainman Streamflow or www.bom.gov.au

When using a climate forecast you should remember that the probability or percent chance of something occurring is just that - a probability. For example if there is a 70% chance of recording more than 100 mm there is also a 30% chance of recording less than 100 mm i.e. 70-30; 30-70. It does not mean that you will get 70% more than 100 mm or 100 mm plus another 70%.

For those who like to follow the relationship between the SOI and rainfall patterns in more detail, have a look at what happened in your area during December to February in the following years since 1950 that have had a Consistently Positive SOI phase at the end of November; 1950, 1955, 1961, 1962, 1964, 1970, 1971, 1975, 1988, 1998, 1999, 2000 and 2007. Find out your average rainfall for December to February and see how many times rainfall was well below, well above or close to average during December to February in the listed years.

The 30 day average of the SOI as of 1 December is plus 16.8. Daily updates on the SOI are available on (07) 4688 1439 or you can receive a text message with the latest SOI values sent to your mobile phone. To subscribe to this free service, call (07) 4688 1459.

The full story

Based on monthly SOI values of plus 14.2 for October and plus 17.4 for November, the SOI has remained in a Consistently Positive phase.

An analysis of historical rainfall records and a Consistently Positive SOI phase at the end of November indicate a reasonable 60 to 80% chance of getting above median rainfall during December through to the end of February throughout the eastern third of Queensland (east of a line running from the bottom of the Gulf of Carpentaria through to the central Darling Downs).

There is a 40 to 60% chance of getting above median rainfall for December to February throughout the rest of the state.

For example Bundaberg has an 80% chance of getting above its December to February median rainfall of 405mm, Proserpine has a 75% chance of getting above its December to February median rainfall of 855mm, Charters Towers has a 73% chance of getting above its December to February median rainfall of 335mm, Toowoomba has a 68% chance of getting above its December to February median rainfall of 353mm, Yuleba has a 65% chance of getting above its December to February median rainfall of 220mm and Longreach has a 55% chance of getting above its December to February median rainfall of 190mm.

For more information on historical rainfall data for your region try Rainman Streamflow or www.bom.gov.au

When using a climate forecast you should remember that the probability or percent chance of something occurring is just that - a probability. For example if there is a 70% chance of recording more than 100 mm there is also a 30% chance of recording less than 100 mm i.e. 70-30; 30-70. It does not mean that you will get 70% more than 100 mm or 100 mm plus another 70%.

For those who like to follow the relationship between the SOI and rainfall patterns in more detail, have a look at what happened in your area during December to February in the following years since 1950 that have had a Consistently Positive SOI phase at the end of November; 1950, 1955, 1961, 1962, 1964, 1970, 1971, 1975, 1988, 1998, 1999, 2000 and 2007. Find out your average rainfall for December to February and see how many times rainfall was well below, well above or close to average during December to February in the listed years.

The 30 day average of the SOI as of 1 December is plus 16.8. Daily updates on the SOI are available on (07) 4688 1439 or you can receive a text message with the latest SOI values sent to your mobile phone. To subscribe to this free service, call (07) 4688 1459.

According to the Bureau of Meteorology ENSO Wrap-Up (available at www.bom.gov.au/climate/enso) a neutral sea surface temperature (SST) pattern can be found in the Pacific Ocean. This is characterised by SST's being close to their long-term average and subsurface ocean temperatures only slightly cooler than normal.

Of interest is that the south east trade winds have been stronger than normal across the western half of the equatorial Pacific. This has contributed to the SOI remaining in positive values for the last few months.

Given the time of year, ocean and atmospheric conditions in the Pacific and the output from six reviewed dynamic climate models a neutral SST pattern is expected to persist through to the end of the 08/09 summer.

The Madden-Julian Oscillation or MJO last transited northern Australia during late November. If its timing remains consistent, the next passage of the MJO is likely to occur during late December. Interestingly a key time to watch for the potential development of cyclones is after summer passages of the MJO.

The MJO is a band of low air pressure which originates off the east coast of central Africa. It travels eastward across the Indian Ocean and northern Australia roughly every 30 to 60 days. Because of the timing of the MJO the phenomenon is also known as the forty day wave. It can be used as an indicator for the timing of potential rainfall events.

The impact of the MJO on rainfall varies between the different seasons and location. For example the MJO has a greater influence on rainfall throughout northern Australia during summer and southern Australia during winter.

When I'm asked about how climate information can be used I refer to a couple of key points developed from client feedback. Key points include that management decisions should never be based entirely on one factor such as a climate or weather forecast. As always, everything that could impact of the outcome of a decision (soil moisture, pasture type/availability, crop and commodity prices, machinery, finance, costs etc) should be considered. For example, the level of soil moisture at planting is the major factor influencing crop yield or success.

A simple cost benefit analysis when making a major decision may also be useful. For example what will I gain if I get the desired outcome? What will I lose (sleep, money, family relationships) if I do not get the desired outcome and what other options (risk neutral) are there? A PART OF THIS PROCESS IS TO HELP MANAGERS TO BE CAREFUL NOT TO CHANGE FROM NORMAL RISK MANAGEMENT TO HIGH LEVEL RISK TAKING BASED ON A PIECE OF INFORMATION (SUCH AS A CLIMATE FORECAST).

Forecasts as well do not always give a strong signal as to likely conditions for your location. In assessing climate forecasts as a management tool consider the level of signal for the key decision times in your location. Rainman StreamFlow is a useful tool for this.

For more information on the seasonal outlook, go to www.longpaddock.qld.gov.au